No. 581] GERM CELLS AND SOMATIC CELL, 



299 



as their conclusions are not based on methods of deter- 

 mining the growth energy of tumors, not suitable for this 

 purpose, in all probability merely the expression of the 

 existence of a number of uncontrolled variable factors. 

 Such factors are numerous and they may explain certain 

 variations observed in growth energy and number of takes 

 in transplantations undertaken at different times or in 

 different mice. There exists, therefore, at the present time 

 no evidence making even probable the existence of 

 rhythms of growth and vitality in somatic cells com- 

 parable to those found in protozoa; neither have thus 

 far been found in somatic cells indications of nuclear 

 changes similar to those periodically occurring in germ 

 cells and probably also in some protozoa and apparently 

 bearing some relation to variations in growth and vitality 

 in these cells. At present we must therefore reckon at 

 least with the possibility that the immortality in somatic 

 cells is not connected with rhythms in vitality and in nu- 

 clear changes of such a character as observed in the other 

 two kinds of potentially immortal cells. 



III. External factors acting on an organism may exert 

 an influence on its germ cells and here produce certain 

 changes which may be transmitted to the following gen- 

 erations, and thus through a number of generations the 

 offspring may show deviations from the type, although 

 the character of the lesions appearing in different gener- 

 ations may not be identical. This has been observed as 

 a result of the action of poisons such as lead and alcohol. 

 Especially the extensive investigations of Stockard on the 

 action of alcohol in guinea pigs demonstrate conclusively 

 that defects appear through several generations. In the 

 case of these injuries transferred to the offspring, it is 

 doubtful whether and to what extent these inheritable 

 defects are characteristic for a certain poison, or whether 

 we have to deal with traumatisms which might be caused 

 in a similar manner by many poisons or even by injurious 

 physical agencies. There is some evidence tending to 

 show that most diverse chemicals may influence embryonic 

 development in a similar manner, that they may produce 



